The primary function of non-compromised, intact skin is to control the various microbes that reside on the skin surface, thus preventing underlying tissue from being colonized by potentially pathogenic species. When a wound occurs, subcutaneous tissue is exposed, leading to a moist, nutritious environment for microbial colonization and proliferation. Wound colonization is often polymicrobial, involving organisms that are potentially pathogenic. If infection occurs, particularly for chronic wounds, the wound may fail to heal. The consequences of this occurrence are traumatic for the patient, with greatly increased medical expenses.
Chronic wounds include pressure ulcers, diabetic foot ulcers, and venous leg ulcers. These wounds are difficult to heal and contribute to persistent individual health problems as well as markedly increasing health care costs. It is believed that bacteria colonizing chronic wounds exist as highly persistent biofilm communities (G. A. James, et al., Wound Repair Regen., 16(1), 37-44, 2008). Biofilm formation appears to be an important contributing factor in delayed wound healing.
It does not appear that the bacteria present on the surface of chronic wounds are present as planktonic cells or even simple primary attachment modes. Rather, such colonization is believed to be by biofilm formation, often of mixed microbial species within a matrix of extracellular hydrophilic polysaccharides. Bacteria living in a biofilm have significantly different properties from planktonic bacteria, as the protected environment of the polymer coating allows them to cooperate and interact. A biofilm has the ability to neutralize host defenses and commandeer host systems, and possesses a vast array of defenses and virulence factors. One feature of this environment is increased resistance to detergents and antibiotics, as the dense extracellular matrix and the outer layer of cells protect the interior of the community.
While biofilms are commonly present on chronic wounds, they are less prominent on acute wounds. Clinically, there is a significant difference in the healing behavior between chronic wounds and acute wounds, with the latter being more facile. Suppression of the biofilm bioburden using multiple simultaneous strategies including debridement, anti-biofilm agents, specific biocides, antibiotics and advanced technologies does enhance wound healing.
Wounds are an ideal environment for the formation of biofilm communities because of their susceptibility to contamination and the availability of substrate and nutrients for biofilm attachment. Chronic wound infections share two important attributes with other biofilm diseases: persistent infection that is not cleared by the host immune system, and resistance to systemic and topical antimicrobial agents. In the absence of a biocidal wound cleanser solution, frequent debridement is often a clinically effective treatment to help heal chronic wounds.
Biofilms reportedly cause an estimated 1 million nosocomial infections each year in the United States. Both aerobic and anaerobic bacteria have been found. Some studies have isolated the most common microorganism (Staphylococcus epidermidis) that triggers biofilm infections, while many other organisms have been isolated. Common bacteria found in biofilms include Gram positive Enterococcus faecalis, Staphylococcus aureus, Micrococcus spp. and beta-hemolytic Streptococcus (S. pyogenes, S. agalactiae) as well as Gram-negative bacteria of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia. 
In addition to biofilms in chronic wounds, biofilms are involved in approximately 90% of all chronic human infections and 65% of all hospital-acquired infections. Biofilms are responsible for otitis media, the most common acute ear infection. Biofilms are also involved in bacterial endocarditis, an infection of the inner surface of the heart and its valves. Biofilms are also found in patients with cystic fibrosis, a chronic disorder resulting in increased susceptibility to serious lung infections. Additionally, biofilms are also reported to be involved with Legionnaire's disease, an acute respiratory infection resulting in Legionnella biofilms, a ubiquitous aquatic organism that can be present in air and water heating/cooling and distribution systems. Biofilms are also involved with periodontal disease, dental plaque, transplant infections, infections of indwelling medical devices (e.g., catheter, prostheses), contaminated clinical surfaces and reusable instruments.
For healing of acute and chronic wounds colonized by microorganisms, proper cleaning is essential. Most commercial wound cleansers are based predominantly upon surfactant cleaning and are designed to soften and remove necrotic tissue and debris. These aqueous solutions have used a surfactant with or without a preservative, with or without a buffer, and with or without a chelating agent.
U.S. Patent Publication No. 2004/0059006 describes a disinfectant composition comprising 1-(2-ethylhexyl)glycerol ether (octoxyglycerin, Sensiva® SC 50) and one or more aromatic alcohols, such as aryloxyalkanols, oligoalkanol aryl ethers or arylalkanols. The composition is said to be useful for controlling mycobacteria. No studies were performed on Mycobacterium biofilms.
U.S. Pat. No. 6,106,854 discusses a liquid that has germicidal and biofilm cleansing properties, comprising an anti-infective, an antiseptic agent, and an anti-biofilm agent, a water purifying agent, a sanitizer and a bactericide, wherein the bactericide includes chlorhexidine, in a concentration of 10.0% to 23.0% of the disinfectant concentration.
U.S. Pat. No. 6,143,244 discusses compositions for cleaning and disinfecting contact lenses wherein a polymeric biguanide is used in combination with bis(biguanides) as disinfectants, which will reduce microbial bioburden by two log orders in four hours and preferably by one log order in one hour. The examples utilize 0.8 ppm (0.00008 wt %) poly(hexamethylene biguanide) and 2 ppm (0.0002 wt %) of alexidine. This low concentration of biguanide is used in a regimen procedure according to FDA Chemical Disinfection Efficacy Test—July, 1985, Contact Lens Solution Draft Guidelines, utilizing bacteria in colony forming units and does not evaluate the efficacy against bacterial biofilms.
U.S. Pat. No. 6,846,846 and U.S. Patent Application Number 2010/0305211 discuss a combination of a biguanide and a branched monoalkyl alcohol, namely octoxyglycerin, (Sensiva® SC 50, glycerol 1-(2-ethylhexyl ether), or 1-(2-ethylhexyl)glycerin), for use as a gentle-acting skin disinfectant. Additional ingredients, particularly quaternary ammonium compounds, and particularly benzalkonium chloride, are shown to be effective against bacteria in colony forming units. This patent and application do not discuss the use of a biguanide and a branched monoalkyl glycol in eliminating a bacterial biofilm.
Octoxyglycerin is sold under the trade name Sensiva® SC 50 (Schülke & Mayr). It is a branched, glycerol monoalkyl ether known to be gentle to the skin and to exhibit antimicrobial activity against a variety of Gram-positive bacteria, such as Micrococcus luteus, Corynebacterium aquaticum, Corynebacterium flavescens, Corynebacterium callunae, and Corynebacterium nephredi. Sensiva® SC 50 is used in various skin deodorant preparations at concentrations between about 0.2 (2,000 ppm) and 3 weight (wt) % (30,000 ppm).
In U.S. Patent Application Number 2007/0287752, an aqueous ophthalmic composition comprising a branched glycerol monoalkyl ether, such as Sensiva® SC 50, present in a total amount of from 0.05 ppm (0.000005 wt %) to 1,000 ppm (0.1 wt %), and an antimicrobial agent, including poly(hexamethylene biguanide) and alexidine, at a concentration of from 0.01 ppm (0.000001 wt %) to 100 ppm (0.01 wt %), with a preference at 3 ppm (0.0003 wt %), where the presence of the branched glycerol compound enhances the biocidal efficacy of the aqueous ophthalmic composition. The compositions are used as a disinfecting solution, a preservative solution or packaging solution for contact lenses. No biocidal studies were conducted on biofilm.
U.S. Pat. No. 7,670,997 discusses an aqueous ophthalmic composition and method of inhibiting the formation of foam in an aqueous ophthalmic composition that includes a surfactant, comprising a branched, glycerol monoalkyl compound and a fatty acid monoester with an antimicrobial agent such as alexidine, chlorhexidine or poly(hexamethylene biguanide). The fatty acid monoester comprises an aliphatic fatty acid portion having six to fourteen carbon atoms and an aliphatic hydroxyl portion, with decanoylglycerol being preferred. In a lens care solution, poly(hexamethylene biguanide) is used in concentration of from 0.01 ppm (0.000001 wt %) to 3 ppm (0.0003 wt %) with alexidine at a concentration of 4.5 ppm (0.00045 wt %), including Sensiva® SC 50 at a concentration of 0.15 wt % (1,500 ppm) and decanoylglycerol at a concentration of 0.12 wt % (1,200 ppm). Synergistic biocidal activity towards colony forming units of Candida albicans and Fusarium solani is reported for interactions of the branched, glycerol monoalkyl compound and the fatty acid glyceryl monoester. No studies were conducted on biofilm with these ingredients.
U.S. Patent Application Publication 2006/0051385 discusses a method of killing or inactivating microorganisms on mammalian tissue by an antiseptic, a hydrophilic component, a surfactant, and a hydrophobic vehicle, where the antiseptic includes biguanides and bisbiguanides. This study did not include an analysis of biofilm elimination.
U.S. Patent Application Publication 2007/0282008 A1 discusses a polymeric biguanide or a bis(biguanide) compound, a chelating agent and a buffering agent for the prevention or treatment of skin and ear tissue infections. The antiseptic behavior of bis(biguanides), such as alexidine and chlorhexidine, and polymeric biguanides, such as poly(hexamethylene biguanide) (PHMB), is discussed for treatment of infection. However, there is no discussion about the incorporation of a monoalkyl glycol, a monoacyl glycerol, or a glycerol alkyl ether, or the interaction of these individual or combined ingredients with a biofilm.
U.S. Patent Application Publication 2009/0202615 discusses compositions containing high concentrations of a surface active agent (surfactant) and a sub-lethal amount of an antimicrobial agent for contacting a microbial biofilm. The Examples utilize high surfactant concentrations (>45%). The sub-lethal amount of antimicrobial agent is defined as less than the standard therapeutically effective amount to effectively eradicate or inhibit the growth of biofilm forming microorganisms or pathogens, or inhibit biofilm formation or eradicate formed biofilms. This application recommends a sub-lethal amount of the antimicrobial agent, such as silver sulfadiazine, to be equal to or less than 1% by weight (10,000 ppm) of the composition. Regrowth of the biofilm was not considered.
U.S. Patent Application 2007/0202006 discusses the use of one or more biguanides to kill bacterial endospores, particularly from the genus Bacillus and the genus Clostridium. This study did not include the use of an antimicrobial vicinal diol. Additionally, biofilm elimination was not considered.
U.S. Pat. No. 5,516,510 discusses deodorant compositions containing poly(hexamethylene biguanide) at a concentration of from 0.01% to 0.5% with a short chain monohydric alcohol, such as ethanol at a concentration of 20-80%, in a nonpolar propellant, which also contains water and a polarity modifier, the latter including dodecanol, 1-(2-ethylhexyl)glycerol ether (Sensiva® SC 50), and ketones such as acetone. The amount of monohydric short chain alcohol and nonpolar propellant can be as high as 99%. There is no discussion on the elimination of a short chain monohydric alcohol or a polarity modifier such as acetone, both of which can cause irritation and stinging on skin, or the use of such a composition to reduce or eradicate biofilm.
The use of commercial wound cleansers that incorporate a biocidal agent have recently gained in importance, particularly to treat wounds highly infected by microorganisms. Three such commercial products include Prontosan® Wound Irrigation Solution and Gel from Braun Medical, Inc., and Microsyn® Skin and Wound Cleanser and Dermacyn® Wound Care from Oculus Innovative Sciences. Prontosan® Wound Irrigation System is based upon a surfactant with the biocide of poly(hexamethylene bisbiguanide) (PHMB). Prontosan® Wound Irrigation Solution and Gel is used for cleansing, moisturizing and decontaminating acute and chronic wounds to aid in efficient wound bed preparation. The Microsyn® and Dermacyn® Wound Care Solution are active oxychlorine compounds and super-oxidized solutions intended for use in the treatment of infection in acute and chronic wounds and in the debridement, irrigation and moistening of acute and chronic wounds, ulcers, cuts, abrasions and burns. Such products are reported to reduce the microbial load and assist in creating a moist environment in order for the body to perform its own healing process. The biocidel activity of such products appears to be based upon a dilute sodium hypochlorite/hydrochlorous acid solution.
While both Prontosan™ and Microsyn® solutions are reported to reduce the biofilm bioburden of wounds, neither has been reported to eliminate regrowth of the biofilm by providing total kill. It is the intent of this invention to provide a solution that is capable achieving this result in order to provide more rapid, more effective wound healing than exists by current methods.